Re: Ariane5 FAQ

["Francisco Malpartida" <fmalpartida@dsl.pipex.com>]

Hi folks

just one little incision on the SW "failure" for Ariane 5.

As mentioned in the thread, the SW was indeed written and tested for Ariane
4.
There are several points which are different from both launchers, one of
which
was instrumental to the events:

Ariane 4 is a vertical launch vehicle where as Ariane 5 is slightly tilted.
Ariane 4
SW was developed to tolerate certain amount of inclination but not as much
as required by Ariane 5. The chain of events are as follows:

    - The on-board SW detects that one of the accelerometers is out of range
        - This causes the redundant CPU to take over.
    - The redundant CPU also detects that one of the accelerometers is out
of range
    which causes the system to advice an auto destruction.

Therefore, the SW behaved as it was supposed to under the conditions it was
designed for.

Cheers


"Vinzent Hoefler" <ada.rocks@jlfencey.com> wrote in message
news:bfhaed$e786b$1@ID-175126.news.uni-berlin.de...
Hyman Rosen wrote:

>Vinzent Hoefler wrote:
>> Obviously you are saying there were any reasons. So could you please
>> explain what they were?
>
>The OP said that there was no reason to assume that the software
>used in the Ariane 4 would work in the Ariane 5. But the designers
>of the Ariane 5 chose to use the hardware and software unchanged,
>so they obviously believed that it would work.

They might have been *believed* that, yes. But for what reasons?

>The OP seems to be saying that just because I can drive my car
>from my house to the supermarket, I have no reason to believe
>that I can drive my car from my house to the video store.

Wrong analogy. They didn't believe that Ariane X would come back from
the supermarket at all. They knew it wouldn't. :-)

Let me try an analogy: If you take the brake controller software from
one car and put it in a different one, what *reason* makes you believe
it would work properly?


Vinzent.